What you need to change is the keyboard Input Method in System Preferences. If you select a language [Spanish, for one, works here] the decimal key on the numeric keypad should insert a comma. Note, of course, that to use your standard keyboard entry you'd need to switch back to the Input Method you normally would use. The switching can be done easily if you check the box in the Prefs to Show Input menu in menu bar.
What Phillip suggested can't work because those settings are for numerical values. The nature of examples you gave do not qualify so are parsed as text strings. The only way those settings possibly could be of use, if at all, is if you wanted to change the Grouping method on a per entry basis every time the number of characters differed.